Background Epidural block is accustomed to clinical anesthesiologist, which is an important part of anesthesia and analgesia. However, it’s operated in blind. The anesthesia effect is estimated by anesthetist after Drug injection or by the feeling of patients, which restrain the development of this technique. Objective To pursue a way as epidural anesthesia indication and to establish an advanced, reliable, objective, controllable, noninvasive monitoring way. Content The ways of auxiliary locating epidural space is reviewed. Trend As the epidural puncture skills changed and the advanced equipments developed, but they are not facilitated in clinic. So an objective position of epidural interspaces would be researched.